Built between 1982 and 1993 as part of the seven-strong Landsort-class mine countermeasures vessels, the last five ships of the class were given a comprehensive midlife upgrade between 2007 and 2010, which resulted in HMS Koster becoming the lead ship of the newly upgraded class of MCMVs.

An identifying feature of the Koster class is the fire control radar on top of the bridge.

In December 2004, the Swedish Navy awarded Kockums a contract for the mid-life upgrade for five of the Landsort class (excluding HMS Landsort and HMS Arholma).

The upgrade includes a new mine countermeasures (MCM) system, adaptations for international operations as well as a new air defence system involving moving and modification of the Arte 726 from the Kaparen class fast patrol boats.

[3][4] The system combines minehunting, minesweeping, mine disposal, surveillance and communication with other naval forces.